Overcurrent/Overdischarge Protection for Lead-Acid Batteries

Abstract: This application note describes the use of a current-sense amplifier with internal dual comparators to monitor and protect against too low battery voltage and too high battery current. While written for lead-acid batteries, the circuit and concept can be extended to NiCd, Li-ion and other battery chemistries.An external power P-channel MOSFET is in series with the battery and its load. It works as a normally closed switch which can be opened if the current-sense amplifier and comparators detect either a high load current OR a low battery voltage. The high current comparator can be latched to detect brief over currents and reset by an external push button.